Efficacy of Seven Invasive-Bermudagrass Removal Strategies in Three Texas Ecoregions

Abstract

Cynodon dactylon (Bermudagrass) is an invasive grass found in some southwestern U.S. grasslands and is linked to decreased wildlife abundance. Cynodon dactylon removal is a necessary first step in many native grassland restoration projects. We evaluated seven C. dactylon removal methods in three Texas ecoregions, seeking to determine which most effectively suppressed C. dactylon growth in varying environmental conditions. We applied treatments to 355-m² plots throughout summer 2015 and measured aboveground, living plant biomass, height, canopy cover, and species richness within plots in April–July 2016. Six treatments reduced (p ≤ 0.05) C. dactylon canopy cover compared to untreated controls at all study sites: single and repeated glyphosate herbicide applications—with or without shredding C. dactylon to 3-cm height two weeks prior, a single imazapyr herbicide application, and a glyphosate, imazapic, and imazapyr herbicide combination all resulted in ≥ 98.60% C. dactylon canopy cover and biomass reduction. A single glyphosate application reduced C. dactylon canopy cover 72.13 ± 27.74% compared to controls. Shredding grass and overseeding Vicia villosa (hairy vetch) reduced (p ≤ 0.05) C. dactylon biomass 49.45 ± 6.92% and height 13.58 ± 0.04% but did not decrease canopy cover relative to controls in any ecoregion. Overseeding V. villosa and shredding C. dactylon prior to herbicide application resulted in greater volunteer plant species richness and greater above-soil biomass. Treatment ability to suppress C. dactylon growth was similar across ecoregions. This implies land managers may use C. dactylon-suppression methodologies standardized for the entire state of Texas and likely beyond. By utilizing our results to effectively suppress C. dactylon, pastures can be prepared for conversion to native rangeland and prairie ecosystems.